1. Field of the Invention
The present invention relates to an apparatus for the optoelectronic detection of switching positions of a mechanically actuatable switching element, and relates in particular to such an apparatus having individual photoelectric receivers, a light source arranged to expose the receivers, and a shutter which is movable relative to the light source and the receivers and is coupled to the movement of the switching element.
2. Background Art
Apparatuses for detecting switching positions are used in switches which are assigned multiple functions in order to allow a user to recognize the switching positions of the multifunction switch. Such switches are used as lighting and steering column switches in motor vehicles. These types of switches are configured to be movable in multiple planes to allow the functions to be executed independently of one another and in parallel to one another. Backlit symbols are assigned to the switch in order to represent the respective switching positions. The symbols light as a function of the respective switch position to indicate the switch position.
These types of switches are conventionally configured as contact switches so that a switch position is attained if the corresponding electrical connection is produced by the switching organ. Even if different functions can be switched with such a multifunctional switch, the cost increases inordinately in case of complicated switch structures if the respective switch positions are to be detected in the above-described visual manner. Moreover, the elements provided for mechanical contact-making are subject to the effects of wear and aging.
In addition to the switch position determination being displayed to a user, the respective switching position should also be made accessible as a data input to a data processing system such as an onboard computer in motor vehicles for monitor and control purposes.
Multifunctional switches can be configured as contactless optoelectronic-functioning switches, as is known from DE 43 32 748 A1. The switch described in this document is characterized in that no electrical contact-making is brought about in order to detect a switching position. Instead, a photosensitive element acting as a receiver is exposed to light if the switching element is in a certain switching position.
An optical switch of this sort includes, besides the photosensitive element, a light source which can be arranged on the same board as the photosensitive element. By means of a fiber-optical member whose area on the light output side is arranged facing the photosensitive surface of the photoelectric element, the required light is brought to the photoelectric element. A movement gap is between the output side of the fiber-optical member and the photoelectric element. A shutter is movable in the movement gap and is coupled to the movement of the switching element to move therewith. The shutter has an opening at a specified position. After a movement of the switching element to a certain switching position, the opening becomes aligned with the area on the output side of the fiber-optical member and the photosensitive surface of the photoelectric element so that the photoelectric element can be exposed to the light.
If the switching element is removed from this position, the shutter shades the photoelectric element from the light and the switching position is exited. In the subject matter of this document, each switching position is thus realized through its own optoelectronic switch. Through suitable arrangement of several such optical switches complicated switching operations can be detected. However, under conditions where installation space is limited, it is not possible to realize complicated switching operations in the described manner.
DE 298 17 668 U1 discloses another switching position detection apparatus which is configured to function in an optoelectronic manner. In the subject matter of this document, a light source is coupled to the movement of the switching element and is thus tracked along with any movement the switching element makes. The light source acts upon a two-dimensional sensor array formed from a plurality of individual converter elements, e.g., a camera sensor. Switching position detection occurs as a function of which converter elements of the sensor array are exposed to light as a function of the position of the switching element. However, this known switching position detection apparatus requires a microprocessor for its evaluation and is thus more expensive than the previously described switching position detection apparatus.
Starting out from the described background art, the underlying object of the present invention is to provide a switching position detection apparatus that can be implemented using simple means while avoiding the disadvantages of the described background art.
This object is solved according to the present invention in that at least two receivers are arranged in each case at a distance correspondingly from each other of at least one switching step in the switching direction of the switching element and that the shutter has a shading region through which in each case of a switching position of the switching element the state of only a single receiver changes when the switching position of the switching element changes to an adjacent switching position.
Moreover, the present invention is characterized by an apparatus for the optoelectronic detection of switching positions of a mechanically actuatable switching element. The apparatus includes a photoelectric receiver, a plurality of light sources arranged to expose the receiver, and a shutter. The light sources and the receiver are movable relative to the shutter and are coupled to the movement of the switching element. The light sources include at least two light sources which are arranged in each case at a distance correspondingly from each other of at least one switching step in the switching direction of the switching element. The shutter has a shading region through which in each case of a switching position of the switching element the state of only a single light source changes its state in terms of an exposure of the receiver when the switching position of the switching element changes to an adjacent switching position.
The switching position detection apparatus according to a first embodiment of the present invention, unlike the known background art, uses a receiver arrangement formed from at least two receivers and a shutter having a shading region. The shading region of the shutter is configured such that in response to each change in the switching position of the switching element only one receiver changes its state. For example, the shading region can be designed such that all of the receivers are simultaneously shaded.
Four switching steps can be detected when using two receivers in a configuration of this sort. At least two receivers are arranged in each case at a distance correspondingly from each other of at least one switching step in the switching direction of the switching element. As the shutter has a shading region with which possibly both receivers can be simultaneously shaded, a switching position is defined in this manner. It is also possible to shade only one receiver, shade only the other receiver, and shade neither receiver with the three other switching positions in a configuration of this sort being defined in this manner.
If four switching steps are provided and if a partial shading of individual receivers is not provided, then only two receivers are required. As such, the number of receivers is reduced by 50% compared to the number of receivers required in the known background art. If partial shading of individual receivers is provided, then the number of required receivers can be further reduced compared to the known background art.
In the present invention, erroneous interpretations are avoided as only a single receiver changes its state in response to a change in the switching position of the switching element to an adjacent switching position. This state change can be caused through exposure of a previously unexposed receiver or vice versa, or also by changing the exposure intensity, e.g., through regional or partial shading of a receiver by the shutter.
The switching position detection apparatus in accordance with a second embodiment of the present invention is similarly configured with the roles of the light source and the receivers being swapped. In the second embodiment, at least two light sources are provided with a single receiver. The light emitted by the light sources is encoded, e.g., pulsed over time. A switching position of the switching element can be detected based on a corresponding evaluation of the received signal. A light encoding can take place, for example, also via a wavelength with different light sources emitting light with different wavelengths.
The switching position detection apparatus according to the present invention is also suitable for carrying out a switching position detection if the switching element is movable in two or more directions. In each direction of movement of the switching element, a receiver arrangement including at least two receivers and the shutter with its shading region is conceived (as described above). Due to the decrease in hardware compared with the known background art, even complicated switching operations can be detected in an optoelectronic manner with a switching position detection apparatus of this sort without the need for a larger installation space.
The use of a microprocessor to use the switching position detection apparatus of the present invention is not necessary as the evaluation can take place via a digital circuit in which the output signal of the switching position detection apparatus feeds into for processing. For example, a digital circuit of this sort can be a binary decoder.
The use of an infrared (IR) light source is preferred for operating the switching position detection apparatus in accordance with the present invention. In a configuration of this sort, in each case a filter which passes IR light is connected upstream of the receivers being used so that the switching position detection apparatus does not need to be encapsulated with respect to otherwise disruptive daylight.
For the case in which a microprocessor is available in the surroundings of the switching position detection apparatus, such as in a motor vehicle, instead of using discrete photoelectric receivers, a sensor array formed from a plurality of individual photoelectric receivers, e.g., a row or camera sensor can be used.